In Nazi Germany, Hitler was quoted as saying "How lucky it is for the government that the people don't think!"  He also emphasized the fact that when speaking to the masses, one should use "sehr venige punkte" or "very simple points", and to repeat them frequently.  The public would eventually believe whatever they were told. 
      There is a difference between to advocate and to lie.  For a politician to advocate for something, is for them to put their best foot forward.  This is a slanting of the issue toward their position, but it is not a deception.  A lie is  to assert something which is not true, or to imply something which is not true.  Unfortunately, modern language has begun to use "spin" as a synonym for lie.  As long as the politician does not actually, technically, specifically lie, then the politician is alright and said to be good at "spin."  These politicians, however, should not be supported. 
      Think of what happens when you walk into a retail store.  You expect the salesperson to be an advocate for their product, and to "spin" or slant the discussion in order to shed the best possible light on their product.  We accept this, and learn to work with it, but if this same salesperson steps over the line and misleads, deceives or even actually lies to us, then we would not and should not tolerate it.  I don't want my politician to have (pardon the expression) diarrhea-of-the-mouth and be incapable of being discreet, or unable to be an advocate for me without telling more than anyone needed to know.  I want a politician who will have the character to stand up and fight for my rights and to be honest with me and those with whom he deals.  I want him to be good at advocating, but not good at lying... and I believe there is a difference.